Apparatus for producing integral finned tubing of fine pitch



T. G. COUNTS May 21, 1968 APPARATUS FOR PRODUCING INTEGRAL FINNED TUBINGOF FINE FITCH Filed Aug. 16, 1965 FlG. 4

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ATTORN United States Patent O 3,383,893 APPARATUS FOR PRODUCING INTEGRALFINNED TUBING OF FINE PITCH Thomas G. Counts, Decatur, Ala., assignor toCalumet & Hecla, Inc., Allen Park, Mich., a corporation of MichiganFiied Aug. 16, 1965, Ser. No. 479,982 7 Claims. (Cl. 72-98) ABSTRACT FTHE DISCLOSURE Apparatus for iinning tubes comprising three arborsprovided with a multiplicity of finning discs and inclined at an anglesuch that two-start fins are produced. The discs are separated by aspacer into groups. The first group is composed of a plurality of pairsof identical discs having peripheral portions the side walls of whichconverge at an angle of approximately 131/2 degrees, the diameters ofthe pairs of discs increasing progressively, and the edge surfaces ofthe pairs of discs being of circular crosssection of progressivelyincreasing radius. The vdiscs of the second group are all ofprogressively increasing diameter and of generally increasingcross-sectional peripheral radius.

It is an object of the present invention to provide a novel arrangementof discs on the arbors for the purpose of Iproducing fine pitch helicalfins on tubing.

More specifically, it is an object of the present invention to providethe discs on eac-h arbor in -two groups which are spaced apart asubstantial distance, the first group of discs constituting a groupeffective principally to displace metal from the fin root spaces, andthe second group effective principally to shape the fin profile.

It is a further object of the present invention to provide the arbors asdescribed in the foregoing with the common perpendicular to the axis ofeach arbor and the axis of the tube being located adjacen-t the firstdisc of the second group of discs on each arbor.

It is a further object of the present invention to provide tube finningapparatus as described in the foregoing in which the first group ofdiscs on each arbor comprises three different sizes of discs and thediscs on the several arbors are arranged such that each space formedbetween each adjacent pair of fins is traversed by three discs of thesame diameter in order.

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying drawings, illustrating a preferred embodiment of theinvention, wherein:

FIGURE l is a diagrammatic elevational view of an arbor containing linforming discs.

FIGURES 2 and 3 are fragmentary elevational views on an enlarged scaleshowing the cross-sectional shape of the peripheral portion of certainof the firming discs.

FIGURE 4 is a diagrammatic view illustrating the relationship vbetween atube being finned and the three i'inning rolls.

FIGURE 5 is `a diagrammatic view illustrating the relationship andsequence of operation of the several discs on the several arbors.

The development of fine pitch integral finned tubing has been madeIpossible by a departure from prior conventional methods of finformation. When employing the usual or standard progression of diametralincreases it was found that the finned tubing was unsatisfactory becauseof root diameter defects or overlays occurred as well as whiskersWhiskers is the term applied to fine 3,383,893 Patented May 21, 1968 ICCslivers of metal which are partially separated from Ithe finned tubingadjacent the roots of the fins. This problem has been overcome byarranging the discs in a particular sequence, by employing a disc as therfirst disc of the second group of discs on one arbor which is smallerthan the last disc of the first group.

The provision of the small disc `as the first disc of the second groupof discs of course changed the tracking relationship of the succeedingdiscs.

The necessity for a change in tracking and cold working relationship ofdiscs is due not only to elongation which Itakes place in the initialstart of -the multiple linning and disc design, but also in thetransition from raw stock diameter to root diameter as the helix anglechanges with the diameter change. Disparities of the two diameters (thatis, raW stock diameter and final root diameter) are great enough thatproper tracking cannot exist from the -raw stock outside diameter tofinal root size.

This development also has required a change in spacer design andlocation. While normal 19-n tubing for example, has employed twospacers, it has been found necessary to use a single spacer for the nepitch or 26-fin production. The spacer is designed to overcome theelongation of the tube created in starting, provide for the tube toreturn to a state of equilibrium, place succeeding discs in properrelationship to the original fins which have so far been produced, andprevent squaring of the tube. Thefspacer location is not only for Ifinformation, but for the necessity of making a continuous diametraltransition from the -beginning raw stock size to root diameter size. Ithas been found that not only the disc arrangement but also the arborlocation is an important factor in permitting commercial production of26-fin tubing.

Referring now to the drawings, there is illustrated in FIGURE 1 an arbor11 having first and second groups of discs 12 and 14 thereon separatedyby a spacer 16. As shown, the assembly of discs and spacers is clampedagainst a radially extending ange 18 on the arbor by suitable means suchfor example as a clamping nut 20 or the like.

In practice, three arbors are employed spaced at approximately1Z0-degree intervals around the path of advance of a tube, a portion ofthe tube being indicated at T in FIGURE 1.

The three arbors are rotated in unison with the tube and due to thecrossed angular relationship, the rotation of the arbors causes the tubeto advance las it rotates, thus forming helical grooves thereon andultimately shaping the metal between adjacent convolutions into the formof effi-cient heat transfer fins. In accordance with the presentinvention the angle at which the axis of the arbor, here indicated at22, crosses with respect to the :axis of the tube T, here designated 24,is such that during one revolution of the tube the tube advances adistance equal to the thickness of two discs. Accordingly, two finformations are produced starting at diametrically opposite points on theend of the advancing tube.

The first groups of discs 12 on the several arbors is primarily for thepurpose of beginning fin formation and produces the major metal movementas the root diameter is formed and pushed down. Once the primary fin isformed the succeeding discs operate principally to control the profileof lthe fins, and the changes produced by the discs in the second groupare accordingly of smaller l magnitude.

Referring to FIGURE 1, it will be observed that the rst group 12 ofdissc comprises six discs, being from starting end two No. 10 discs, twoNo. 9 discs, and two No. 8 discs. Intermediate the groups of discs 12and 14 is the cylindrical spacer 16. The sec-ond group of discscornprises a single relatively small No. 10 disc, followed in order bydiscs in the sequence: Nos. 7, 6, 5, 4, 3, 2, 1, 1. It will be observedfrom the figure .that the arbor is disposed such that a lineperpendicular to the axis 22 of the arbor and also perpendicular to theaxis 24 of the tube T is adjacent the No. 7 disc of the second group ofdiscs, this point being indicated in FIGURE 1 at 26.

Referring now to FIGURES 2 4and 3, in FIGURE 2 there is diagrammaticallyshown at 2S the elevational view of a portion of the periphery of onelform of disc, this being the type of ldisc used for discs Nos. 7-16. Itwill be observed that the extreme edge of the disc is relatively narrowand that its sides are inclined at a substantial angle. It may bementioned at this time that all of the discs are of identical thicknessat their central portions.

Referring to FIGURE 3, there is illustrated at 30 the other type of discwhich is used in producing the discs Nos. 6-1. This disc differsessentially from the disc having the peripheral portion 28 in that it isrelatively wider at the extreme periphery, and its side portions aretapered at a lesser angle.

The significant changes from disc to disc is represented in the tablebelow, where diameter of the discs is represented by D, the radius ofcurvature of the peripheral cross-section is represented by R, and theangle of the sides by F.

Diam. D Radius R Angle F (degrees) 2. 062 010 5 2. 060 010 5 2.057 009 52. 054 00S 5 2. 050 007 M 2A 045 007 7 2. 040 O06 9 2. 029 006 13% 2.024 0055 13% 1. Q95 .005 13% than the increase in diameter between thefinal or lower numbered discs. Thus for example, the difference indiameter between the consecutive sizes of discs from the No. 6 to theNo. 1 disc may decrease from about .006 to about .002 inch. On the-other hand, the difference in diameter between the No. and the No. 9disc may be approximately .O inch, and the increase in diameter betweenthe No. 8 and the No. 7 disc may 4be about .010 inch.

Not only are the consecutive discs of increasing height, but their shapeis also modified so as to produce a thinning and Adesired shaping of thematerial of the fins as it is formed outwardly by displacement.

In describing the disc forming roll shown in FIGURE 1, this was intendedto be typical and in practice two differently constituted iin formingrolls are provided. The roll shown in FIGURE l is unique and theremaining two rolls didier in the omission of lthe relatively small No.10 disc which constitutes the rst disc of the second group 14 of discs.

Referring now to FIGURES 4 and 5 there is illustrated the exactarrangement of discs on the arbors and the arrangement of the rolls withrespect to the tube.

Referring rst to FIGURE 4, the tube is illustrated at T with a partiallyformed n F thereon. The .tube is shown in simultaneous Contact withdiscs on three arbors identified respectively as A1, A2 and A3. In thisfigure the direction of rotation of the tube and arbors is asillustrated and it will therefore be observed that any particular pointon the tube moves in sequence from discs carried by the arbor A1 todiscs carried by the arbor A2 and the discs carried by .the arbor A3.

Referring now to FIGURE 5 there is illustrated diagrammatically thearrangement of the several discs on the several arbors, and in addition,the special relationship between the arbor is indicated. In this figurethe arbors A1, A2 and A3 yare identified. It will be observed that thearbor A2 has the rst group 12 of discs made up in the sequence 10, 1G,9, 9, 8, 8. The space-r 16 has a length which is approximately 7.2 timesas great as the width of each of the discs. This causes the discs of thesecond group 14 to engage with a minimum of axial stress the spaceslbetween adjacent fins as they have been formed by the discs of thefirst group. The second group 14 of discs on arbor A2 is made up ofdiscs in the following sequence: 10, 7, 6, 5, 4, 3, 2, 1, 1.

The arrangement of discs on the arbors A1 and A3 are identical. The lefthand or first group of discs 12 on these arbors is made up of discs inthe following sequence: 10, 10, 9, 9, 8, 8. Identical spacers 16 areemployed on all arbors. On the arbo-rs A3 and A1, the second group ofdiscs 14 is made up with the following sequence of discs: '7, 6, 5, 4,3, 2, 1, 1.

It will thus be seen that the second group of discs on the arbor A2differs from the second group of discs 0n the arbors A1 and A3 in theprovision of a small No. 10 disc as the rst disc of the second group.

It will be understood that in order to provide doublestart helicaliinning the second No. 10 disc on the arbor A2 will initiate formationof a fin space at a point 180 degrees from the start of the n spaceformed by the left hand disc No. 10. In other words, the advance of thetube due to the angular relationship of the arbors is such that when thestart of the helical space, groove or `channel initiated by the lefthand disc No. 10 has reached a point degrees, or at the dia-me-tricallyopposite side of the tube from the arbor A2, then the second No. 10 discon the arbor A2 will initiate its operation.

From the foregoing, and from a consideration of FIG- URE 4, it will lbeobserved that the sequence of spaces yon any particular area of the tubewith respect to the arbors is A2, A3, A1, A2, A3, etc. In FIGURE 5 thereis a diagram illustrating the sequence of operation of the several discson the several arbors to produce the helical grooves on the tube, thegrooves of course providing the fins therebetween. In this figure thefull lines S1, S2, S3, etc. indicate the progression of a groove orspace formed by the rolls, and the dotted lines connecting the ends ofthe full lines merely represent the travel or advance of the groove orspace as it is being formed from the arbor A1 to the arbor A2.

From the foregoing it will be observed that one of the two continuoushelical -grooves or ychannels formed by the rolls is acte-d on in thefollowing sequence: Left hand disc No. 10 on arbor A2, left hand discNo. 10 on arbor A3, left hand disc No. 10 on arbor A1, left hand discNo. 9 on arbor A2, left hand disc No. 9 on arbor A3, left hand disc No.9 on arbor A1, left hand disc No. 8 on arbor A2, left hand disc No. 8 onarbor A3, left hand disc No. 8 on arbor A1, disc No. 7 on arbor A2, discNo. 6 on arbor A3, disc No. 6 on arbor A1, disc No. 5 on arb-or A2, discNo. 4- on arbor A3, disc No. 4 on arbor A1, disc No. 3 on arbor A2,`disc No. 2 on arbor A3, disc No. 2 -on arbor A1, disc No. 1 on arborA2, disc No. 1 on arbor A3, and disc No. 1 on arbor A1. Therefore, thesequence of action of the differently sized discs in producing theillustrated groove of FIGURE 5 is: 10, 10, 10, 9, 9, 9, 8, 8, 8, 7, 6,6, 5, 4, 4, 3, 2, 2, 1, 1, 1. Similarly, the other groove which isformed by the discs is acted on by differently sized discs in thefollowing sequence: 10, 10, 10, 9, 9, 9, 8, 8, 8, 10,7, 7, 6, 5, 5, 4,3, 3, 2, 1, 1, 1.

From the foregoing it will be apparent that each groove is initiallyformed by engagement with three discs No. 10, three discs No. 9, threediscs No. 8', and in the second group lby a progression of discs fromNo. 7 to No. 1 with two identical discs acting in sequence intermediateaction between single discs of selectively smaller and larger sizerespectively.

From the Itable presented in the yforegoing it will be observed that theincrease in `diameter `between successively sized discs, starting withthe small disc No. 10, is .029, .005, .011, .005, .004, .003, .003, and.002. In general terms it will be observed that the amount by whichsuccessive discs increase in diameter diminishes toward -the finishingsection of each arbor. Similarly, it will be observed that the radiusdetermining the shape of the entering edge portion of the successivediscs, commencing with the small disc No. 10, increases as follows:.0005, .0005, no change, .0010, no change, .0010, .0010, .0010, nochange.

Similarly, it will ybe observed that the angle F between the sides ofthe edge portions of the discs, starts at the relatively large value of131/2 degrees for discs Nos. 10-8 and thereafter, decreases successivelyto 9 degrees for disc No. 7, 7 degrees for disc No. 6, 51/2 degrees fordisc No. 5, and 5 degrees for discs Nos. 4-1.

With this arrangement the entry of the discs into the material of thetube is facilitated while the shaping of the discs in the second groupresults in proper forming of the fins. The foregoing arrangement isessential in the production of the exceptionally fine pitch finned tubesto which the present invention relates.

The drawing and the foregoing specification constitutes a `descriptionof the improved apparatus for producing integral finned tubing of finepitch in such full, clear, concise and exact terms as to enable anyperson skilled in the -art to practice the invention, the scope of whichis indicated by the appended claims.

What I claim as my invention is:

1. Apparatus for forming exceptionaly fine pit-ch helical fin formationson tubing which comprises three arbors positioned with their axes spacedlaterally from and substantially equally spaced around the axis alongwhich a tube advances during a progressive finning operation anddisposed at a small angle with respect thereto, a plurality of finningdiscs mounted on said arbors for rotation therewith, said discs being ofgenerally increasing diameter in the direction of advance of the tube,of increasing peripheral cross-section radius of curvature,

and of decreasing angularity between peripheral portions of the sidewalls of the discs, a spacer on each of said arbors providing axialseparation between a first and a second group of discs, said arborsbeing disposed at the angle at which their axes cross the axis ofadvance of the tube such that continuous two-start helical finning isproduced, the discs of the first group to engage a given portion of anadvancing tube being provided in a plurality of pairs of identicaldiscs, the second group on each arbor comprising discs of progressivelyincreasing diameter from disc to disc.

2. Apparatus as defined in claim 1 in `which the included angle betweenthe side portions adjacent the periphery of all discs making up thefirst groups of discs is approximately 27 degrees.

3. Apparatus as defined in claim 2 in which the included angle betweenthe side portions adjacent the periphery of the last several discs ofthe second groups is approximately 10 degrees.

4. Apparatus as defined in claim 1 in which the first disc in the secondgroup of discs on one of the arbors is a relatively small diameter dischaving substantially the same diameter as the first disc of the firstgroups of discs, the first discs of the remaining two second groups ofdiscs on the remaining two arbors being of larger diameter than the lastdisc in the first groups of discs.

5. Apparatus as defined in claim 1 in which the average differencebetween the diameters of adjacent discs decreases progressively in thedirection of tube advance.

6. Apparatus as defined in claim 1 in which the discs have edge portionsof circular cross-section, the radius of curvature of the cross-sectionof the edge portions of the discs increasing in the direction of tubeadvance from about .0050 to about .0100".

7. Apparatus as defined in claim 6, the radius of curvature increasingby about .0005" between adjacent discs in the first group and by about.0010 between most of the different sized discs in the second group inthe direction of tube advance.

References Cited UNITED STATES PATENTS 2,868,046 l/1959 Greene 72-98FOREIGN PATENTS 852,368 10/1960 Great Britain.

RICHARD I. HERBST, Primary Examiner.

